Conduits such as pipes frequently contain fluids, which may be at a pressure greater than ambient pressure. The fluids and the pressure may be maintained within a conduit by one or more fittings such as valves which are associated with the conduit. If such fittings are removed or become compromised, leakage of fluid and/or pressure from the conduit may result.
A conduit as described above may be associated with any source of fluid and/or pressure. In some circumstances, the conduit may be in fluid communication with a storage tank, such as an oil storage tank, so that the fluid in the conduit originates from the storage tank and the pressure in the conduit is due to the pressure head of the fluid within the storage tank.
In order to perform maintenance or repair on the conduit or its associated fittings, it is desirable to avoid a loss of fluid and/or pressure from the conduit.
A first option is to remove the source of fluid and/or pressure by disconnecting the conduit from the source of fluid and/or pressure or by draining a storage tank to which the conduit may be connected. This first option may be effective in eliminating or reducing fluid and/or pressure leakage, but is potentially time consuming, inconvenient and expensive, since it may require temporarily removing equipment from operation while the conduit is maintained or repaired.
A second option is to seal the conduit upstream of the location at which the maintenance or repair is taking place so that the location of maintenance or repair is isolated from the fluid and/or pressure. This second option typically requires a seal assembly which may be delivered through the conduit to a position upstream of the location of maintenance or repair and which can be selectively actuated to temporarily seal the conduit at the desired position.
Apparatus and methods exist which enable a seal assembly to be inserted into the conduit at a position downstream of the location of maintenance or repair, to be moved upstream past the location of maintenance or repair, and to be selectively actuated to temporarily seal the conduit upstream of the location of maintenance or repair. Once the maintenance or repair is completed, the seal assembly may be selectively actuated to unseal the conduit and the seal assembly may be removed from the conduit.
Examples of such apparatus and methods may be found in U.S. Pat. No. 2,690,612 (Scott), U.S. Pat. No. 2,867,243 (Bowan), U.S. Pat. No. 3,841,355 (Laner), U.S. Pat. No. 4,597,147 (Henry), U.S. Pat. No. 5,592,965 (Rakieski), U.S. Pat. No. 6,581,620 (Babcock et al), U.S. Pat. No. 6,755,216 (Mostala), France Patent Application Publication No. FR2566873 A1 (Keriolet), France Patent Application Publication No. FR2670558 (Gillodts), and PCT International Publication No. WO 2010/112067 A1 (Ornetzeder).
Of the above apparatus and methods, U.S. Pat. No. 4,597,147 (Henry) and U.S. Pat. No. 5,592,965 (Rakieski) contemplate some of the challenges which exist in designing an apparatus which is capable of being passed through a fitting such as a valve and which may be used with valves having valve ports of varying geometries.
There remains a need for apparatus and methods for sealing a conduit to facilitate maintenance or repair of the conduit or its associated fittings, wherein the apparatus includes a seal assembly which may be introduced into the conduit from a position downstream of the location of maintenance or repair, which may be moved upstream past the location of maintenance or repair, which may be selectively actuated to temporarily seal the conduit upstream of the location of maintenance or repair, and which may be selectively actuated to unseal the conduit after completion of the maintenance or repair so that the seal assembly can be removed from the conduit.